1. Field of the Invention
The present invention relates to an improved process for the preparation of etherified polyoxyalkylene derivatives by reacting the corresponding free hydroxy compound with a dialkyl sulfate in the presence of an aqueous solution of an alkali metal hydroxide. More specifically, the present invention is directed to an improved method for preparing methyl ethers of polyether polyol employing dimethylsulfate as a methylating agent.
2. Description of the Prior Art
It is known that polyoxyalkylene compounds having one or more terminal hydroxyl groups can be etherified by first converting the free hydroxy compound with an alkali metal, an alcoholate, a hydride or a hydroxide of an alkali metal into the corresponding alkali metal alcoholate and then further reacting the alcoholate with an alkylating agent, such as, dialkyl sulfate or an alkyl halide.
German Patent Application No. 2 800 710 discloses a process for the preparation of etherified polyoxyalkylene compounds in which the free hydroxy compound is treated with an organic halide, such as butyl chloride in the presence of an aqueous solution of sodium hydroxide or potassium hydroxide whose initial concentration is of sodium or potassium hydroxide is not less than 30 percent by weight. The process of the German disclosure is carried out at a temperature of from about 80.degree.-100.degree. C.
European Patent No. 302487 discloses a process for the preparation of etherified polyoxyalkylene derivatives by reacting the corresponding free hydroxy compound with a dialkyl sulfate in the presence of an aqueous solution of an alkali metal hydroxide. The reference discribes a two-step process where it is essential to add reactants in a two-step process to form the etherified polyoxyalkylene derivative. The present invention relates to a single step process wherein improved yields and substantial savings in time and costs are realized.
East German Patent No. 244 549 discloses a process for etherification of oligoglycol monochlorides which is characterized by the fact that the oligoglycol chlorides are reacted with dialkyl sulfates in the presence of an inorganic base at temperatures usual for alkylation reactions. The ethers produced are useful for pharmaceutically active substance, surfactants and pesticides.
Hay, U.S. Pat. No. 3,402,144, discloses a process to metalate polyphenylene ethers with alkali metal alkyls or aryls to give activated alkali metal-containing polymers. These metalated polymers readily react with chemical reagents to produce modified polymers, and also react with anionically polymerizable monomers to produce graft copolymers.
Leverett, U.S. Pat. No. 3,393,179, discloses a process for the preparation of a high molecular weight polyoxymethylene alkyl ether which consists of contacting the unetherified polymer with a combination of dimethyl or diethyl sulfate and an orthoester in a process which does not require the addition of a base or acid to catalyze the reaction. The reaction temperature is in the range of 100.degree. C. to 180.degree. C. and preferably is carried out in an inert hydrocarbon medium.